(107) Frequency and Trends of Pre-Pandemic Surge Periods in U.S. Emergency Departments, 2006-2019

Introduction: While truly large-scale surge events are rare, less severe but still-impactful acute and subacute surge periods occur or may occur due to a wider range of etiologies including respiratory viral outbreaks, extremes of weather, and mass trauma. We sought to quantify the frequency, outside of the pandemic setting, with which individual health care facilities are faced with surge periods due to severe increases in demand for emergency department (ED) care.

Methods: We performed a retrospective cohort study of publicly-available pre-pandemic U.S. ED data from 2006-2019 from the all-payer, nationally representative Nationwide Emergency Department Sample (NEDS) from the Healthcare Cost and Utilization Project (HCUP). We standardized the volume of ED visits for each ED-month to the median volume of ED visits for that facility and calendar month. We defined surge periods a priori as ED-months in which an individual facility ED saw a greater than 50% increase in ED visits per month above the facility-/calendar month–specific medians.

Results: During 2006-2019, 3,317 U.S. EDs reported 354,534,229 ED visits across 142,035 ED-months. 57,495 (40.5%) ED-months during the study period had a 0 to 50% increase in ED visits that month above facility-specific medians and 1,952 (1.4%) ED-months qualified as surge periods and had a greater than 50% increase in ED visits that month above facility-specific medians. These surge months were experienced by 397 (12.0%) unique facility EDs. Compared to 2006, the most proximal pre-pandemic period of 2016-2019 had a notably elevated likelihood of ED-month surge periods (ORs 2.36-2.84, all p < 0.0005). Compared to the calendar month of January, the winter ED-months in December through March have similar likelihood of an ED-month qualifying as a surge period (ORs 0.84-1.03, all p > 0.05), while the non-winter ED-months in April through November have a lower likelihood of an ED-month qualifying as a surge period (ORs 0.65-0.81, all p < 0.05).

Conclusions: Understanding the frequency of surges in demand for ED care—which appear to have increased in frequency even before the COVID-19 pandemic and are concentrated in winter months—is necessary to better understand the burden of potential and realized acute surge events and to inform cost-effectiveness preparedness strategies.